The present invention is directed to a process for preparing compounds of the general formula (I).

Compounds of the general formula (I) are advantageous precursors for preparing phospholane catalysts, especially bisphospholane catalysts. The invention therefore likewise provides such compounds, and also for the use of the substances in question for preparing these catalysts.
Enantiomerically enriched chiral ligands are used in asymmetric synthesis and asymmetric catalysis. An essential factor here is that the electronic properties and the stereochemical properties of the ligand are adjusted optimally to the particular catalysis problem. An important aspect of the success of these classes of compound is attributed to the creation of a particularly asymmetric environment of the metal centre by these ligand systems. In order to utilize such an environment for effective transfer of chirality, it is advantageous to control the flexibility of the ligand system as an inherent limitation of the asymmetric induction.
Within the substance class of the phosphorus-containing ligands, cyclic phosphines, especially the phospholanes, have achieved particular significance. Bidentate chiral phospholanes are, for example, the DuPhos and BPE ligands used in asymmetric catalysis. In the ideal case, however, a variously modifiable chiral ligand template is available, which can be varied within a wide range in relation to its steric and electronic properties.
The preparation of, for example, bidentate chiral phospholanes is effected generally by reacting the finished phospholane units with the catalyst backbone (WO2005/049629; EP1490379; DE102005014055). A successful method in this context works with phospholanes trialkylsilyl-substituted on the phosphorus atom, which are reacted with correspondingly halogen-substituted backbone compounds, for instance by the following scheme:

A further route is the reaction of aromatic-(PH2)2 compounds which are reacted under base catalysis with compounds of the following type (EP0592552, U.S. Pat. No. 5,329,015).

In the preparation routes described, the starting compounds are accordingly backbone compounds (see above) which possess very good nucleofugic leaving groups, or oxidation-sensitive phosphine-substituted aromatic systems are used.